1. Field of the Invention
The field of the invention is concerned with tools used to insert and extract printed circuit boards into and out of apparatus housings. It is more specifically concerned with such tools having a mechanical advantage to supply the necessary forces to engage and disengage multiple pin connections between the printed circuit board and the backplane connector of the apparatus housings.
2. Description of the Prior Art
Many tools operative to insert and extract printed circuit boards into and out of apparatus housings are essentially a handle substitute. These handle substitutes are adapted to attach to brackets on the printed circuit board and provide the convenience of a ready handclasp to apply the inserting and extracting forces. Examples of this handle substitute type tool are disclosed, for instance, in the U.S. Pat. Nos. 3,484,129, issued to S. G. Askren on Dec. 16, 1969; 3,617,083, issued to J. V. Koppensteiner on Nov. 2, 1971; and 3,903,576, issued to S. Stein on Sept. 9, 1975. The tools disclosed therein are essentially U-shaped detachable handles which are engaged with the printed circuit board to insert and extract it from the apparatus housing. These handles have two main component members, one being nested within the other, and slidable against a spring bias to activate connecting means which interlock with brackets on a printed circuit board.
No mechanical advantage to multiply an applied force is provided, the chief convenience being the provision of a ready grip.
In the instance of printed circuit boards having multiple pin connections between the board and the backplane of the apparatus housing, a mechanical advantage is a necessity. Forces necessary to engage and disengage multiple pin connectors may attain magnitudes as high as 75 pounds.
U.S. Pat. No. 3,178,214, issued to W. G. Tinkelenberg on Apr. 13, 1965 discloses a tool to insert and extract printed circuit boards from apparatus housings and includes operational features to provide a mechanical advantage to the extracting force. This tool is basically a combination handle and lever which has the same width as the printed circuit board. Two hooks at the outer edges of the tool are adapted to engage the outside corners of the printed circuit board. The tool is rotated about a heel structure which is located adjacent to the connecting hooks in order to apply an extraction force to the printed circuit board with mechanical advantage. This extracting force applied to the printed circuit board is sufficient to disengage the connecting pins of the connector of the printed circuit board from the backplane of the apparatus housing.
While this tool provides a mechanical advantage for extraction purposes, it serves merely as a handle for insertion purposes. In the case of a multiple pin connector, insertion forces can easily equal the force magnitude needed for extraction purposes.
Each of the tools described in the above reference requires careful positioning to engage the tool with a printed circuit board bracket. Two connecting devices must be lined up with receiving devices attached to the printed circuit board. Only one of these tools (described by Tinkelenberg) has mechanical advantage in applying force and this mechanical advantage occurs only in the extracting mode of operation.
A suitable tool for engaging and disengaging printed circuit boards having multiple pin connectors should have mechanical advantage in both insertion and extraction modes of operation to supply the necessary force which can easily reach 75 pounds. Further desirable attributes include ease of connection and disconnection of the tool from the printed circuit board, and compactness for easy storage.